1. Field of the Invention
The present invention relates to a vehicle air conditioner having a front air-blowing structure for blowing air toward a front seat side of a passenger compartment and a rear air-blowing structure for blowing air toward a rear seat side of the passenger compartment.
2. Description of Related Art
In a conventional vehicle air conditioner, for improving both heating performance for heating air blown toward the foot area of a passenger and defrosting performance of a windshield in the winter, an inside/outside air double layer flow mode (hereinafter, referred to as "double layer flow mode") is set so that circulated inside air having a high temperature is blown from a foot opening and outside air having a low-humidity is blown from a defroster opening.
For example, in an air conditioner described in JP-A-10-109520 by the applicant of the present invention, a warm air bypass opening and a warm air bypass door are disposed at an immediately downstream position of a heating heat exchanger, and a front foot opening and a rear foot opening are provided at a downstream air side of the warm air bypass opening in an air flow direction. When the double layer flow mode is set during a maximum heating, the warm air bypass opening is opened by the warm air bypass door, and an air passage immediately downstream from the heating heat exchanger is partitioned by the warm air bypass door into a first air passage through which outside air flows and a second air passage through which inside air flows.
However, during a temperature control area, the double layer flow mode is removed, and the warm air bypass door closes the warm air bypass opening. In this case, warm air having passed through the heating heat exchanger flows upwardly and is mixed with cool air bypassing the heating heat exchanger, and thereafter, mixed air is blown toward the foot opening. Thus, during the temperature control area, pressure loss is increased due to a bent air flow. Because a duct having a relative small sectional area is used as a rear foot duct connected to a rear foot opening due to an arrangement space in a vehicle, an air amount blown toward a rear seat side in a passenger compartment is greatly decreased during the temperature control area. Further, because the rear foot duct is necessary to have a long distance pipe from an air conditioning unit disposed at a vehicle front side to a rear seat side, heat loss becomes larger in a rear foot duct, and temperature of air blown toward the rear seat side becomes lower. As a result, heating capacity for the rear seat side of the passenger compartment becomes insufficient. On the other hand, even during a cooling mode, because a long rear face duct from the air conditioning unit to a rear seat side is also necessary, cooling capacity for the rear seat side of the passenger compartment becomes insufficient.